As urban centers increase in size, and traffic congestion becomes more common, the need for accurate and up-to-date traffic information also increases. Traffic surveillance relies primarily on traffic sensors, such as inductive loop traffic sensors that are installed under the pavement. Alternatively, video sensors may also be used to obtain traffic information.
Residing underground, inductive loop sensors are expensive to install, replace and repair because of the associated roadwork required. Moreover, such roadwork also causes traffic disruptions. Video sensors, on the other hand, are cheaper, but have other drawbacks, such as an inability to operate in the dark or in weather that impairs visibility, such as fog or snow.
To overcome these drawbacks, radar sensors have been employed to obtain traffic information. Radar sensors typically transmit low-power microwave signals at the traffic, and detect vehicles based on the reflected signals. Radar sensors are generally cheaper than inductive loop traffic sensors, and, unlike video sensors, operate well in the dark and in a wide range of weather conditions.
For convenience and cost effectiveness, it is desirable that radar sensors be capable of operating in the field for many years without requiring maintenance. Thus, there is a need for radar sensors for obtaining traffic information that can function for extended periods of time outdoors, with little servicing.